Our Design Verification Testing of the mock-up from the leaky $6.6 million San Francisco home continued Wednesday with water- or “storm-” testing.
In this series, following procedures from ASTM E 331, Matt Travis, Design Verification Testing Specialist; Ron Tatley, inventor of the Design Verification Test Chamber; and Courtney Murdock, PROSOCO’s Director of Project Testing, ramped up the chamber from a simulated 25 mph wind-driven rain shower to a full-blown 150 mph — per the instructions of the architect who sent in the mock-up.
As I mentioned in yesterday’s post, litigation is involved in this investigation of the house’s failed building envelope. That’s why I’m not using names of the architect or the home-owner who hired the architect.
The mock-up featured everything found in the walls of the home itself, including stucco cladding, a window, building papers, and electrical- and air conditioning penetrations. The contractor who’s been hired to repair the house built the mock-up.
Matt and Ron installed the mock-up on the small side of the chamber. The stucco “outside” of the mock-up faces into the chamber where it gets “rained” on from the chamber’s spray racks. The mock-up’s plywood and wood stud side faces out.
If, or rather, when the water from the spray racks penetrates the exterior, you can plainly see it coming through the wood.
Wednesday’s test procedure called for 15 minutes of exposure to spray at increasing air pressures. The increased pressure corresponds to various wind speeds. In this test, Matt and Ron pumped air into the chamber to simulate 15 minutes exposure to rain at 25 mph, 33 mph, 70 mph, 100 mph, 125 mph and 150 mph.
During each 15-minute test, Matt, Ron and Courtney closely inspected the wall for water coming through.
After 15 minutes, they shut the machine down for five minutes. Then they fired it back up to the next-higher pressure/wind speed, as specified by E 331.
Each time they discover a leak, Ron and Matt investigate until they find the leak’s origin. Where it shows up on the plywood and stud side of the mock-up isn’t necessarily where it entered on the stucco side.
Each time they find a leak, Matt plugs it with PROSOCO R-GUARD Emergency Water Stop. The blue paste temporarily seals the leak while vividly marking the spot.
At just under 10 minutes of simulated 100 mph wind-driven rain, the latest water penetration shows up. It’s coming from an electrical box penetration about halfway up the wall. The penetration is flashed with a peel and stick on the exterior-facing side of the plywood, and there’s a flange over that, but none of the edges of the peel and stick or the flange were sealed to the wall.
In this test, water didn’t get in at lower pressures. At 100 mph, however, water goes up as well as down, and finds its way into all sorts of places you’d never guess it would. The house being investigated, it turns out, often faces 100 mph wind-driven rain.
That’s the lesson Design Verification Testing teaches. Water doesn’t always do what you think it will. Materials don’t always behave the way you think they will, especially when conditions turn extreme… and there are few places that don’t experience extreme weather, sometimes at least.
These leaks are actually pretty small, Ron says. The trouble is that they don’t stay that way. Each wetting causes successively more deterioration, especially if the wall can’t dry out — such as when it’s got an impermeable vapor barrier installed.
It isn’t a poorly built wall by typical standards, Ron said. It’s just that typical standards almost always let water in at some point. By building and testing for the specific conditions the structure will face, instead of “typical standards,” you can make sure you don’t find yourself in lawsuit-land, helping to feed the multi-billion dollar construction litigation industry — like the builder of the home we’re checking out now.
# # #